1. Field of the Invention
The present invention relates generally to fryers and methods of using such fryers. In particular, the present invention is directed to fryers which deactivate before a level of a cooking medium in the fryer falls below a minimum level, and methods of deactivating such fryers.
2. Description of Related Art
Known fryers, e.g., open-well fryers and pressure fryers, are used to cook various food products, e.g., poultry, fish, or potato products. Such fryers include a cooking vessel, e.g., a fry pot, and the cooking vessel is filled with a cooking medium, e.g., an oil, a liquid shortening, a meltable-solid shortening, or water. Such fryers also include a heating element, e.g., an electrical heating element, such as a plurality of heating coils, or a gas heating element, such as a gas burner and gas conveying tubes, which heat the cooking medium in the cooking vessel. After the cooking medium reaches a preset temperature (herein after referred to as the “cooking temperature”), the food product is placed into the cooking medium, such that the food product is cooked in the cooking medium. For example, the food product may be positioned inside a container, e.g., a wire basket, and submerged in the cooking medium for a predetermined amount of time sufficient to cook the food product. The amount of time sufficient to cook the food product at a given cooking temperature depends on the type of food product which is cooked. Moreover, the cooking medium is used during several cooking cycles before the cooking medium inside the cooking vessel is replaced or is supplemented with a new or filtered supply of cooking medium.
When the same cooking medium is used during several cooking cycles, a level of the cooking medium inside the cooking vessel gradually decreases. For example, a portion of the cooking medium may evaporate or may be absorbed by the food product. The level of the cooking medium inside the cooking vessel is an important factor in the efficiency of the fryer. For example, when the level of the cooking medium is too high, placing the food product inside the cooking vessel may cause the cooking medium to overflow or to boil over the walls of the cooking vessel. Moreover, when the level of the cooking medium is too low, or if the cooking vessel is empty, the heating element may overheat the cooking vessel, which damages the fryer or reduces the efficiency of the fryer, or both.
In order to monitor the level of the cooking medium inside the cooking vessel, such known fryers include an apparatus which senses the level of the cooking medium. For example, in such known fryers, a plurality of fluid level sensors, e.g., float switches, capacitive level sensors, proximity switches, pressure switches, strain gauges, or optical refractive sensors, may be affixed to an interior surface of the cooking vessel at various levels within the cooking vessel. As such, each fluid level sensor is positioned at a predetermined level within the cooking vessel and determines whether cooking medium is present at that particular level.
Such known fryers also include a controller which is electrically coupled to each of the fluid level sensors, and the controller deactivates the heating element of the fryer based on the level of the cooking medium inside the cooking vessel. The controller also may implement one of several control modes. For example, the controller may implement a first control mode when the fryer is cooking the food product, and a second control mode when the temperature of the cooking medium is greater than or equal to the cooking temperature, but the fryer is not cooking the food product. The controller also may implement a third control mode when a user is cleaning the fryer, and a fourth or an idle control mode to maintain the temperature of the cooking medium between the cooking temperature and a temperature of air within the cooking vessel. For example, the controller may apply the idle control mode when the fryer is not in continuous use, but customer demand for the food product may increase without desired or sufficient notice to the user of the fryer. Moreover, the controller may implement a fifth or a melt control mode when the temperature of the cooking medium is relatively cold, e.g., when a difference between the temperature of the cooking medium and the temperature of air within the cooking vessel is less than or equal to a predetermined temperature difference. The purpose of the melt control mode is to heat the cooking medium without burning the cooking medium, and to protect the cooking vessel by limiting the amount of heat which the heating element applies to the cooking medium, e.g., by discretely or non-continuously applying heat to the cooking medium, or by gradually increasing the heat applied to cooking medium.
Nevertheless, such fluid level sensors are relatively expensive, which increases the cost of manufacturing the fryer. Further, when such fluid level sensors are submerged in a cooking medium at the cooking temperature, the fluid level sensor may become inaccurate or unreliable. Moreover, using the melt control mode when the temperature of the cooking medium is significantly below the cooking temperature may increase an amount of time to raise the temperature of the cooking medium to the cooking temperature. The melt control mode also may increase the number of control modes which the user of the fryer selects from when operating the fryer.